1. Field of the Invention
This invention relates to a process for fabricating a semiconductor device and, more particularly to a process for forming a contact and a wiring layer.
2. Related Arts
The so-called blanket CVD-W (tungsten) technique has recently been considered to be promising for plugging up a microscopic contact hole having a diameter of 0.5 .mu.m or less which is formed in a SiO.sub.2 insulating layer on a silicon substrate.
Attention has also been attracted to the use of tungsten for a wiring layer in light of its reliability.
Usually an adhesive layer such as of TiN, TiW and WSi.sub.2 is formed by sputtering in order to enhance the adherence of a tungsten layer to a SiO.sub.2 layer and to prevent chemical reaction of the tungsten layer with a Si substrate when tungsten is deposited.
In the above conventional method, however, when the above adhesive layer is directly formed within a contact hole of a high aspect ratio, a problem of Si attack occurs due to poor step coverage of the adhesive layer. Accordingly, it has been proposed to use a CVD-tungsten silicide film having good step coverage properties for the adhesive layer. Nevertheless, the adherence of such a film to the SiO.sub.2 insulating layer and to the Si wafer constituting the bottom of a contact hole is not so good, causing a problem of film peeling when the tungsten layer exerting significant stress is deposited.